Text rule trends

"""An extract.py plugin: each dependency named in a package.json is one item.

  python3 extract.py SAMPLE --extractor plugin --plugin package_deps.py:items --kind-map '{"package\\.json$": "package.json"}'

The function gets one version's file body and returns a list of item strings.
Bodies that are not package.json (or not valid JSON) give no items.
"""
import json


def items(body):
    try:
        pkg = json.loads(body)
    except ValueError:
        return []
    if not isinstance(pkg, dict):
        return []
    out = []
    for field in ("dependencies", "devDependencies", "peerDependencies"):
        for name in (pkg.get(field) or {}):
            out.append(f"{field} {name}")
    return out